1. Field of the Invention
The present invention relates to wireless communication jammers in environments where inhibiting wireless communications is desired and further relates to wireless communication jammers that prevent wireless communication devices such as cell phones, two way radios, smart phones, WiFi enabled computers and devices, and personal digital assistants from communicating. The category of the present invention is sometimes referred to in the prior art as wireless communications jamming, RF jamming, radio frequency jamming, cell phone blocking, and/or cell phone jamming.
2. Description of Related Art
Wireless communications devices have become increasingly common. At times, it is desirable to block wireless communications from occurring in specific areas. An example of an area that may require communication device blocking are the facilities within prisons where inmates are housed. Areas that require blocking are referred to as target areas when deploying a wireless communications jammer.
Wireless communication jammers are utilized by government agencies with legal authority to permit or deny usage of the wireless frequency spectrum. An industry for wireless communication jamming devices has developed in response to these needs. A number of wireless communication jamming technologies have developed and advances in technologies have occurred.
Most prior art wireless communication jamming systems are comprised of a signal generation device which feeds a signal into a power amplifier which in turn feeds a transmitting antenna. The transmitting antenna emits radio frequency signals on the same frequencies that the target wireless device uses. This interferes with the reception of the target signal and prevents the target wireless device from communicating.
FIG. 1 is a block diagram of the typical prior art wireless communications jammer system including a signal generator 1, a power amplifier 2, an optional output filter 3, and a transmitting antenna 4. The components of the jamming system with exception of the transmitting antenna are typically housed together in enclosure 5.
The most common type of prior art wireless jamming is barrage jamming in which a jamming signal is produced which sweeps across the entire target frequency band. A barrage type jamming system has the advantages of being simple and effective and remains effective over time even if the target signals within the jammed frequency band change frequencies or protocols. The disadvantage of a barrage type jammer is that it is relatively inefficient in that the output power of the jammer is spread across frequencies that do not require jamming. This results in lower jamming effectiveness and increased heating of the power amplifier. The increased heating of the power amplifier is detrimental to the reliability of the jammer.
A second type of prior art jammer exists and is called a frequency specific jammer, where the jammer produces jamming signals only on the frequencies within the target frequency band that require jamming. The signal generators of these systems use digital technology. This type of system has the advantage of producing higher output power at the target frequencies. The disadvantage of this type of system is that it must be pre-programmed with the exact frequencies that require jamming. This pre-programming requirement increases the cost of deploying such a system. This type of system also has the disadvantage of being less reliable over time because the specific frequencies and protocols used within a target frequency band often change. A third disadvantage of this type of system is that the signal generation circuitry is more complex resulting in an inherent decrease in reliability.
A variation of the barrage type jammer and the frequency specific jammer is the reactive type jammer. This type of jammer produces jamming signals only when a target signal is detected. This type of jammer can be a barrage type jammer or a frequency specific jammer. This technology has the advantage of increasing the efficiency of the power amplifier and jamming system. The disadvantage of this type of jammer is that it increases the complexity to the system. This additional complexity increases the cost of the system and decreases reliability. Another disadvantage of the reactive type jammer is that it is not always effective against short burst communications because of the delay between the time of detection of the target signal and the commencement of the jamming signal in response.
For all types of jamming systems, the effectiveness of the system is constrained by the output power of the jammer power amplifier. In order for a jamming to occur, the jamming signal power must be higher than the power level of the target signal.
Spread spectrum wireless communication technologies such as CDMA and WCDMA are becoming increasingly common because of their increased spectral efficiency when deployed in a cellular environment. Spread spectrum communication is inherently difficult to jam. This increased use of spread spectrum protocols is increasing the need for greater jammer efficiency.
Cell phone and many other wireless communications protocols make use of a frequency division duplexing scheme where a frequency range is dedicated for transmissions from the base station to the mobile communications device and a separate frequency range is used for transmissions from the mobile device to the base station. The communication that occurs from the mobile device to the base station is called the uplink communication and the communication from the base station to the mobile device is called the downlink communication. Properly designed jamming systems must take into account the specific uplink or downlink frequency bands that require jamming.
There is a need for a wireless communication jammer that incorporates a signal generation method that has the simplicity and reliability of a barrage type jammer but that also provides the greater efficiency provided a frequency specific and reactive jammer. There is also a need for a jammer signal generation method that provides greater efficiency in jamming spread spectrum type signals such as CDMA and WCDMA.